To correct a time difference with a timepiece of normal use while travelling, we must move the hands each time after a complicated calculation of the time difference. It is extremely troublesome and inconvenient because we have to check with the radio time signal if we want exactness. Many devices for the solution of this problem have been attempted up to now, but none of them is definitive. One of the many devices, best for the solution, I believe, is to move the dial instead of the hands for adjusting the time differential. This system is partially adopted on a watch by R. Corp. of Switzerland, which has a 24 hour hand in addition to the 12 hour hand and a 24 hour dial ring around its main body. But with this watch, we have to read the time from two separate hands on two different hour dials. This is, in fact, not different from using two watches, one of a 12 hour system and another of a 24 hour system, together. Other timepieces currently in circulation, called "World Time Clocks" are worthy of use whenever information on the times in foreign countries is needed whilst remaining in the home country, but not useful when visiting different places while travelling or using there in daily life. The same system is adopted on a wrist watch of T. Corp. of Switzerland, but the indication of the time in the foreign country is too complicated to read and inconvenient for the traveller's use.
The timepiece of this invention is based exclusively on the 24 hour system, and this is it's most distinctive characteristic from the timepieces in common use today. However this idea of the 24 hour system is not novel and has really existed since the medieval age. For instance, in Italy in the 15th century, an example of a clock of this type was represented in a wall-painting by Botticelli, and Paolo Uccello did a decoration on the wall-clock in the cathedral of Florence which we can still see today. This type of clock has really been known a very long time, but the examples were confined to rather large scale clocks such as those found in public places like cathedrals or those for putting on a desk. Later, the clock became smaller than before and the 12 hour system has become common especially for the portable watch. In this century, the 24 hour system watch has been made for people engaged in special fields such as transport, but it has not been produced to supply popular demand. The 24 hour system has become usual all over the world in traffic time-tables; nevertheless, this has not brought about a drastic change in daily customs or in watches themselves. This seems to indicate that people have not found any necessity as yet for changing the 12 hour system of dividing a day into a.m. and p.m.: first of all, this custom appears to be firmly entrenched in our lives and secondly, most people seem to have a certain "affection" for a 12 hour system watch because of it's simplicity. However, the situation can be changed, if the following two points can be achieved: firstly, if people are offered a timepiece with a novel function realizable only through the 24 hour system, and secondly if the difficult problem of design can be solved.